1. Field of the Invention
The present invention relates to a dynamic speaker, and particularly to a structure for fixing a voice coil to a diaphragm in the dynamic speaker.
2. Description of the Related Art
As one type of a speaker, a dynamic speaker has been known heretofore. The dynamic speaker, as disclosed in, for example, JP-A-6-178390, comprises generally a diaphragm, a voice coil of which one end portion is fixed to the diaphragm, and a magnetic circuit unit defining a cylindrical magnetic gap for placing the other end portion of the voice coil therein.
As the fixing structure of the voice coil to the diaphragm, the following structure is known, as disclosed in the JP publication. One end portion 2a of a voice coil 2 having an I-shaped coiling section as shown in FIG. 10A is bonded and fixed to a diaphragm 4.
However, in the speaker having such a fixing structure, since the large bonding area cannot be obtained, the fixing strength is insufficient. Accordingly, there is fear that the voice coil 2 peels off and separates from the diaphragm 4 during being used. Particularly, in case that the speaker is mounted on an automobile or the like, since it is used under environment where considerable vibration and shock load are applied, the voice coil 2 is easier to separate from the diaphragm.
On the other hand, as shown in FIG. 10B, in case that the coiling thickness of the voice coil 2 is set large, the relatively large bonding area between its one end portion 2a and the diaphragm 4 can be obtained, whereby the sufficient fixing strength can be obtained.
However, in this case, since a width of a cylindrical magnetic gap G of a magnetic circuit unit 6 becomes large, there is a problem that electroacoustic conversion efficiency of the speaker degrades. Further, the larger the coiling thickness of the voice coil 2 is, the larger the weight of the voice coil 2 becomes, whereby the large load acts on the bonding surface. Therefore, there is also a problem that separation preventing effect cannot be obtained as expected.
The invention has been made in consideration of these circumstances, and an object of the invention is to provide a speaker in which separation of a voice coil can be prevented without worsening acoustic characteristic of a dynamic speaker.
In order to achieve the object, a predetermined coil supporting member is provided in the invention.
Namely, there is provided a speaker comprising:
a diaphragm;
a magnetic circuit unit defining a cylindrical magnetic gap;
a voice coil having a first portion fixed to the diaphragm, and a second portion placed in the cylindrical magnetic gap; and
a coil supporting member, fixed to the diaphragm, for supporting the first portion of the voice coil,
wherein the coil supporting member is caulked and fixed to the diaphragm by subjecting a caulking projection formed in the coil supporting member to a plastic deformation.
The xe2x80x9cdiaphragmxe2x80x9d, xe2x80x9cvoice coilxe2x80x9d and xe2x80x9cmagnetic circuit unitxe2x80x9d are not particularly limited in their concrete constitution such as their material, shapes, and the like as long as they can be used as components of the dynamic speaker.
The xe2x80x9ccoil supporting memberxe2x80x9d, as long as it supports the first portion of the voice coil in a state where it is caulked and fixed to the diaphragm by a plastic deformation of its caulking projection, is not particularly limited in its concrete constitution such as its material, its shape, a supporting method of voice coil, or the like. Further, the xe2x80x9ccaulking projectionxe2x80x9d, as long as the coil supporting member can be caulked and fixed to the diaphragm by its plastic deformation, is not particularly limited in its concrete constitution such as its shape, its size, the number of the projections, arrangement, or the like.
As described in the constitution, in the speaker according to the invention, the coil supporting member that supports the first portion of the voice coil is caulked and fixed to the diaphragm by subjecting the caulking projection formed in the coil supporting member to the plastic deformation. Therefore, the following effects that act on the invention can be obtained.
Namely, since the voice coil is supported by the coil supporting member at the first portion thereof, it is not only directly fixed to the diaphragm by bonding but also indirectly fixed to the diaphragm through the coil supporting member. Therefore, the sufficient fixing strength of the voice coil in relation to the diaphragm can be obtained even if the coiling thickness of the voice coil is not made large and the large bonding area is not obtained between the first portion of the voice coil and the diaphragm unlike the conventional art. Hereby, since it is not necessary to expand the width of the cylindrical magnetic gap in the magnetic circuit unit, it is possible to prevent electroacoustic conversion efficiency of the speaker from lowering.
Further, since the coil supporting member is caulked and fixed to the diaphragm by the plastic deformation of its caulking projection, the diaphragm itself does not receive the excessive load at the caulking time. Accordingly, by providing the coil supporting member, it is possible to prevent deformation injurious to the acoustic property from occurring in the diaphragm.
As described above, according to the invention, the separation of the voice coil can be prevented without worsening acoustic property of the speaker.
In the constitution, in case that the fixing strength of the voice coil to the diaphragm is sufficiently obtained by only the support of the coil supporting member, the direct fixing between the voice coil and the diaphragm by bonding may be omitted. In this case, since the bonding step or the like required conventionally when the voice coil is fixed to the diaphragm can be eliminated, the working efficiency in manufacture of speaker can be heightened greatly.
In the constitution, in case that a flange portion protruding inward in the radial direction is formed at one end portion of the voice coil, and an engaging portion that engages with this flange portion is formed in coil supporting member, the voice coil can be surely supported by the coil supporting member, so that the fixing strength of the voice coil to the diaphragm can be sufficiently heightened. Therefore, the direct fixing between the voice coil and the diaphragm by bonding can be readily omitted.
In this case, the xe2x80x9cflange portionxe2x80x9d and xe2x80x9cengaging portionxe2x80x9d, as long as the coil supporting member can support the voice coil by their engaging, are not particularly limited in the concrete constitution such as a sectional shape.
The concrete method of subjecting the caulking projection of the coil supporting member to the xe2x80x9cplastic deformation isxe2x80x9d not particularly limited. For example, the plastic deformation can be also performed by a mechanical method such as cold caulking. Further, in case that the coil supporting member is composed of a member made of synthetic resin, a method can be also adopted, in which the caulking projection is subjected to a heat deformation by applying the ultrasonic vibration to the caulking projection.
By adopting the method in which the caulking projection is subjected to the heat deformation by applying the ultrasonic vibration to the caulking projection, even in case that a speaker is a small-sized speaker and a caulking projection of its coil supporting member is very small, caulk-fixing can be performed readily and reliably.
In this case, since the diaphragm itself is not subject to caulk-fixing, it is not necessary entirely to take application of material of two members to fusion-bonding into consideration like a case where the two members are fusion-bonded by an ultrasonic wave. Accordingly, there is not restriction on selection freedom of material of the diaphragm, because the method in which the caulking projection is subjected to the heat deformation by applying the ultrasonic vibration is adopted.
As described above, the concrete constitution of the coil supporting member is not particularly limited. Further, in case that this coil supporting member is composed of an annular member, the caulking projections are formed at plural places in the coil supporting member at a predetermined distance in the circumferential direction, and plural through-holes into which these caulking projections are inserted are formed in the diaphragm; caulk-fixing can be performed in a state where the coil supporting member is exactly positioned in the predetermined position of the diaphragm.
As described above, in case that the flange portion protruding inward in the radial direction is formed at the first portion of the voice coil and the engaging portion that engages to this flange portion is formed in coil supporting member, the voice coil can be reliably supported by the coil supporting member. Therefore, also in case that fixing of the coil supporting member to the diaphragm is performed by other fixing methods than caulk-fixing, for example, by bonding, the fixing strength of the voice coil in relation to the diaphragm can be heightened in some degree.